Recently viewed a window project in the photo forum and thought I might pass this info on to anyone planning a similar project... When adding a vinyl window to a bimini or sail, first measure and bast the vinyl in place using double face basting tape. When you are happy with its position sew it in place using a 6mm stitch(or longest stitch you can get with your machine) one quarter inch in from the edge. Don't cut the hole first because you stand a good chance of getting bias stretch in your bimini or sail with the material removed. This can really hurt the shape of a sail and will look wrinkled in a bimini. After the vinyl is sewn in place turn the bimini or sail over and measure one inch inside the stiching. Now cut the material out and fold the one inch under all around and stitch around the edges. You now have a double stitch completely around the vinyl. This is a very simple job and is also very strong and has no bias stretch. Don't worry if your window is over a seam in the bimini or a spot where two sail panals come together. It won't hurt a thing. Happy sewing and sailing.. Ron/KA5HZV